In roof construction for buildings and residences, various types of roof assemblies have been used to protect the interior of the building from precipitation and other outdoor elements. In one common example, a roof assembly includes at least one solid structural layer, typically made of plywood, covered by a plurality of shingles formed from asphalt, metal, tile, and other materials. It is also common to insulate the underside of the solid structural layer to provide a thermal barrier between the external environment and the interior of the building. However, it is well understood that moisture or moist air may seep into the insulation from edges or seams of the roof assembly. Consequently, these roof assemblies are believed to perform best when the underside of the solid structural layer is ventilated with an air flow that tends to remove any moisture from the insulation. This ventilation prevents or substantially eliminates mold growth and degradation of the insulation.
One particular design for ventilating a roof assembly is referred to as a vented nail base (VNB) roof assembly. These VNB roof assemblies include a first structural layer connected to the framework of the building, a second structural layer configured to receive shingles (e.g., the solid plywood panels), and an insulating layer between the first and second structural layers. The insulating layer may include one or more roof insulation panels such as foam insulation panels laying over the first structural layer. In order to provide a ventilating layer of air space between the foam insulation panels and the second structural layer, wooden block spacers have been inserted at various locations between the insulation panels and the second structural layer. This arrangement is described in further detail below with reference to FIG. 3.
However, these wooden block spacers suffer from several drawbacks. First, the wooden block spacers transmit the entire load of the second structural layer and the shingles directly onto the insulating layer. To this end, the structural support for the second structural layer and the shingles relies on the strength of the insulating layer. As a result, the structural support for the second structural layer and the shingles is relatively weak between wooden block spacers and along any edges of foam insulation panels used to form the insulating layer. Additionally, each of the wooden block spacers must be separately positioned and coupled to the foam insulation panels and/or the second structural layer, which is a tedious and time consuming process.
There is a need, therefore, for a roof assembly and a method of installing a roof assembly that addresses these and other drawbacks of current vented nail base roof assemblies.